DEVELOPMENT OF TKICHOGRAMMA EVANESCENS. 175 
Discussion. 
The Significance of the Nuclear Changes during 
Blastoderm Stage. — Many nuclei (from twenty-five to 
fifty-five) are cast out altogether. Others, as far as I can tell 
all of them, extrude the microsome or small chromatin 
granule, marked GRC. in PI. 11, figs. 16 and 21. In some 
cases there are two granules of the same size, both of which 
are expelled into the cytoplasm. No granule can be found 
to be extruded from the germ cells, and it might follow 
therefore that the latter, at this period at least, contain 
more chromatin than the ordinary blastoderm nucleus. In 
Miastor, Kahle (5) and Hegner (3) have described a definite 
chromatin diminution process whereby the somatic nuclei are 
deprived of a part of their chromatin during certain divisions. 
Though I do not overlook the possibility of a homologous 
occurrence taking place in Tricliogramma evanescens, 
I am more inclined to believe that another explanation 
should be attached to the remarkable chromatin diminution 
in the parasite. In the first place the chromatin diminution 
in Miastor takes place quite early, before the blastoderm is 
formed completely, and, moreover, the process is brought about 
in a different manner, not by extrusion of a granule, but by the 
discarding of the larger part of the chromosomes during the 
mitotic division, only the extreme ends of the chromosomes 
going to the opposite spindles at the telophase. The residual 
mass in the middle of the spindle undergoes degeneration. 
No satisfactory explanation of the occurrence in Miastor 
has been advanced, bat in Trichogramma evanescens I 
would suggest that the process is connected with the curious 
metabolic influences which must affect the nuclei. It must be 
remembered that all nourishment which is necessary for the 
development of the egg, and which is ordinarily provided 
by the central mass of yolk of the insect-egg, is, in the case 
of this parasite, derived from the yolk of another insect’s 
egg and without the aid of vitellophags. Such nourishment 
